In this short talk during a Direct Response Advertising conference, advertising executive David Ogilvy, who founded advertising agency Ogilvy & Mather, talks about his secret weapon that established his agency in just six months – direct mail, or direct response advertising.

From Harry Brignull's blog "90 Percent of Everything" (one of Brignull's readers pointed out that the video is probably from the 80's):

Here's a wonderfully dated video of David Ogilvy giving what looks like a keynote address to a (by video, which must have been breathtakingly modern back in the 1960s).

Ogilvy came from a background in research, and was an early proponent of AB testing. He had a huge amount of respect for the Direct Response Advertising industry (as opposed to what he called 'General Advertising' – Print, TV, etc.) – mainly for the fact that they were so focused on tracking response rates, and working towards winning ad designs.